1. Field of the Invention
The invention relates to a lifting mechanism for an exercise apparatus, and more particularly, to a lifting mechanism that makes a linear telescopic motion rather than a spiral rotation. Moreover, the unloaded portion of the lifting mechanism is made of lightweight material to meet the requirements on weight and strength.
2. Description of the Related Art
Most of the conventional exercise apparatuses includes a lifting mechanism to adjust its inclination relative to a horizontal plane. In order to facilitate the operation thereof, a motor is employed to drive a reduction gearset for imparting rotational motion to a lifting element. In this way, a desired angle is achieved.
As shown in FIG. 1, a lifting mechanism 80 for a treadmill 60 includes a motor 81 that drives a reduction gearbox 82 pivotally attached to a tread base 61 to bring a spindle 83 in rotation. The spindle 83 is telescopic within an elongated socket 84 with its bottom end pivotally attached to a base frame 62. The lifting mechanism 80 features that the height above the socket 84 is adjustable by rotating the spindle 83, thereby undergoing a folding or an unfolding action of the tread base 61. The supporting force required grows in proportion as the inclination of the tread base 61 increases and the contact area between the spindle 83 and the socket 84 decreases. Due to the restricted space between the tread base 61 and the base frame 62, the extension of the spindle 83 is limited to a certain extent. Therefore, the torque of the whole spindle 83 is concentrated at the top 841 of the socket 84, thereby resulting in vibration of the tread base 61 and even malfunction thereof. Thus, the service life thereof is reduced. Besides, the spindle 83 during its rotation is exposed to the outside, and this would endanger the operator or others around him. In addition, it's not easy to cover the spindle 83 for a greater safety since it undergoes the extending or the retracting action. Meanwhile, it's difficult and costly to cut a screw thread into the inner wall of the socket 84.
In order to eliminate the above-mentioned disadvantages, the inventor of the invention has tried to install a rotational socket with which the spindle makes a linear telescopic motion without rotation. This has been proved applicable. However, the reduction gearbox 82 must have a sufficient strength to withstand the torque created by the spindle. Therefore, the reduction gearbox 82 must be made of metal material, and this will increase the whole weight thereof, thereby affecting the installation and movement of the treadmill. Moreover, the production cost of the treadmill is increased in addition to its weight.